Known in the state of the art is a solution described in U.S. Pat. No. 7,741,839 introducing the general principle of an absolute position sensor using a magnet generating a continuously variable field and a magnetic sensor delivering two electric signals representative of the magnetic components with a sinusoidal shape so as to determine the relative position of the magnet and the sensor. This patent proposes performing an arctangent calculation of the ratio between the signal delivered by the two sensors to provide an approximate position of the movable magnet. In this way, the angle of the magnetic field is measured directly at the measuring point.
The precision of the angle thus determined is not satisfactory since, in the general case, the two components of the magnetic field have very different amplitudes. As a result, the angle of the magnetic field calculated by the arctangent and the evolution of the position are not proportionate, which then leads to great imprecisions in knowledge of the position. The geometric configurations making it possible to obtain equality between the components are limited or require a significant impact on the bulk, as for example described in U.S. Pat. No. 7,030,608.
In order to improve the precision, a solution has been proposed in French patent FR2893410 consisting of applying a gain coefficient to the ratio of the signals delivered by the sensors, and a probe having two pairs of Hall elements associated with a flux concentrator. This prior art patent describes a sensor having a cylindrical magnet that is magnetized along its diameter. Detection elements are positioned on the periphery of the magnet and sense the evolution of the tangential and radial components of the magnetic field. In order to be able to decode the actual angle of rotation of the sensor, a corrective gain is applied that is equal to the ratio of the maximum amplitudes of the voltage from the tangential component to the voltage from the radial component. In this way, the non-linearity of the obtained signal is improved. However, this configuration is limited to the case of the diametrically magnetized ring.
This solution was completed by the invention described in European patent EP1989505. This patent describes a linear or rotary sensor having a magnet whereof the variation of the magnetization direction within the magnet is linearly variable. In this way, still by applying a standardization factor equal to the ratio of the amplitudes between the voltage from the radial and tangential fields, it is possible, via an arctangent calculation, to determine the angular or linear movement of the probe relative to the magnet. However, in many cases, in particular when the magnetization harmonics are significant or when the magnetization done in the material does not evolve over a whole period, applying this simple ratio does not make it possible to obtain precise enough position information.